It has been common practice for many years at attack of dry rot in buildings to replace all of the woodwork in which dry rot has been detected. This is obviously an expensive procedure, if the attack is extensive.
Attempts have previously been made to avoid such a replacement by exterminating living organisms, such as vermin, plants and/or microorganisms causing the destruction of the woodwork, by treatment with electromagnetic waves.
DE patent No. 855 331 thus discloses how to treat the attacked woodwork or brick work by means of so-called HF or UHF radiation, whereby the harmful organisms (vermin or plants) are killed. It appears from the publication and the pertaining drawings that UHF or rather microwave radiation is used by the method in question and that the woodwork is exposed to microwave radiation.
DE patent No. 937 200 discloses a method for the extermination of vermin or vegetation harmful to wood in building structures, and in particular dry rot, whereby a new attack also is prevented. By the method described through-going holes are drilled in the structural parts and heating cartridges are inserted heating the structural parts by means of electrical resistance heating, whereafter the boreholes are filled with a chemical preservative.
DE 1 936 502 also discloses a method for the extermination of harmful organisms in buildings, whereby the attacked area of the building is heated by means of microwave energy from an energy source placed within the attacked area. The energy source may be magnetron. It is stated that a temperature of approximately 40.degree. C. sustained for 10 minutes is sufficient to exterminate dry rot and a temperature of 65.degree. C. sustained for 1 minute is sufficient to exterminate woodworm.
Furthermore, it is known to wrap up the entire building in a dense material and then keep the house heated at a very high temperature--about 50.degree. C.--for one or several days.
However, this method is very expensive, partially due to the costs in connection with the mounting and dismounting of the insulation around the house and the mere heating and partially due to the damage, which the intensive and prolonged heating may sustain to the other materials and contents of the house. Thus, the household effects have to be removed to a great extent to avoid damage during the heating.
Furthermore, it is known from SE published specification 412 878 to heat woodwork to be preserved with chemical wood preservatives by radiating the woodwork with electromagnetic waves. However, the object of the method is to provide an improved penetration and dispersion of the chemical preservative.
Moreover, it is known to heat wood by means of HF generators, whereby so-called capacitive high-frequency stationary systems are used for drying and heating of a range of non-metallic materials, in particular for drying of wood, yarns, for glueing of furniture and bookbinding articles, for drying of sand cores in foundries, and for welding of plastics.
Furthermore, it is known to expose living tissue to electromagnetic radiation to combat pathogenic or morbid growths such as cancer.